LOS ANGELES -- The search for a former police officer suspected in three killings could heat up Sunday as authorities announce a reward that could reach $1 million for information leading to an arrest.

The manhunt for Christopher Dorner, 33, stretched into its fourth day Sunday with a scaled back search of a mountain resort area, now covered with snow, east of the city. Dorner's burned-out Nissan pickup was found Thursday, and authorities said remnants of camping gear and weapons were found in the charred vehicle on a forest road in the Big Bear area of San Bernardino County..

Dorner is wanted in connection with a double homicide and the killing of a police officer in a rampage that police say stems from his dismissal from the Los Angeles Police Department in 2008.

Police are investigating a taunting phone call that Dorner may have made to the father of the woman they believe he killed. Monica Quan, a week ago. Two law enforcement officers who requested anonymity because of the ongoing investigation told The Associated Press they are trying to determine who made the call to Randal Quan, a retired Los Angeles police captain, days after the killing.

The caller allegedly told Randal Quan that he should have done a better job protecting his daughter. Monica Quan was found dead of multiple gunshots with her fiance in a car outside their Irvine condominum.

"Hopefully the reward will motivate people that may be involved with assisting him or might be reluctant to talk to us to call us and to put an end to this," Los Angeles police Sgt. Rudy Lopez said. Officials were trying to raise up to $1 million dollars, according to LAPD Cmdr. Andrew Smith.

Officials will re-examine allegations by Dorner, that his law enforcement career was undone by racist colleagues, Police Chief Charlie Beck announced Saturday. While he promised to hear out Dorner if he surrenders, Beck stressed that he was ordering a review of his 2007 case because he takes the allegation of racism in his department seriously.

The Los Angeles Police Department has a troubled racial legacy. A community of online sympathizers has formed, echoing complaints against police that linger in some communities. One Facebook page supporting Dorner said "this is not a page about supporting the killing of innocent people. It's supporting fighting back against corrupt cops and bringing to light what they do."

In his rambling manifesto, Dorner cited a string of perceived injustices, discrimination and slurs leveled his way from childhood to his brief service in the Los Angeles Police Department as a motivation for his revenge rampage aimed at law enforcement.

Beck said he has directed the department's Standards Bureau and his special assistant for constitutional policing "to completely review'' a complaint Dorner brought against his training officer that led to the internal board hearing and his termination for false statements. He said it would include "re-examination of all evidence and a re-interview of witnesses.''

"We will also investigate any allegations made in his manifesto which were not included in his original complaint,'' said Beck, whose force has long been an object of complaints from minority communities, but which has also been praised by community leaders for reforming itself over the past decade.

Beck, in explaining his actions, said, "I am aware of the ghosts of the LAPD's past and one of my biggest concerns is that they will be resurrected by Dorner's allegations of racism within the Department.''

"But, I also know that we are a better organization now than ever before; better but not perfect,'' Beck wrote. "Fairness and equality are now the cornerstones of our values and that is reflected by the present diversity of the department. We are a majority of minorities, almost exactly reflecting the ethnic makeup of Los Angeles.''

"As hard as it has been to change the culture of the Los Angeles Police Department, it has been even more difficult to win and maintain the support of the public. As much as I value our successes in reducing crime, I value even more our gains in public confidence,'' Beck said.

Police swarmed into the Big Bear mountain community in the San Bernardino mountains Thursday after Dorner's burned-out pickup truck was found. They followed his tracks until losing them.

On Saturday, helicopters with heat-sensing technology were aloft searching for any thermal clues to Dorner in the mountains.

A spokeswoman for the Irvine police, who were taking the truck as evidence in their double-murder investigation, said the truck's axle appeared to have been damaged. But Lt. Julia Engen said Saturday that it was unknown whether the damage occurred before the fire, when Dorner was driving it on a remote, unpaved forest road, or when it was towed from the forest by authorities Thursday afternoon.

Cindy Bachman, spokesperson for the San Bernardino County Sheriff's Department, told reporters that Dorner's mother owns undeveloped property in Arrowbear, about 35 miles away from the scene. She said authorities searched and cleared that site.

Also, newly released surveillance video showed Dorner tossing several items into a Dumpster behind an auto parts store on Monday. The store's manager told FOX5 in San Diego that an employee found a magazine full of bullets, a military belt and a military helmet. Majid Yahyai said he and the employee took the items across the street to a police station.

Earlier Friday, another warrant was served at a house belonging to Dorner's mother. Officers collected 10 bags of evidence, including five electronic items.

In his online manifesto, Dorner vowed to use "every bit of small arms training, demolition, ordnance and survival training I've been given" to bring "warfare" to the LAPD and its families.

The chairman of the review board that heard Dorner's case told the Orange County Register that he is under police protection and has not been able to leave his home and family because of Dorner's threats.

"I haven't been able for the last few days to go outside my house,'' Capt. Phil Tingirides told the newspaper. "Am I afraid? Well, I hesitate to use the word... but I saw what he did to his attorney.''

"I recognize by being the chairman of the board that read the final verdict, he will be equally enraged by my part in it,'' Tingirides said.

Police said they had created a multi-agency task force to handle the Dorner case, including the Los Angeles, Irvine and Riverside police departments, FBI, US Marshals and other law-enforcement agencies.

The manhunt, however, was not confined to the mountainous areas. Thousands of heavily armed police remained on the lookout throughout California, Nevada, Arizona and northern Mexico for a suspect they say is bent on revenge and willing to die.

Randy Quan was the first Chinese-American to attain the rank of captain on the LAPD force, the department has said. He practiced law after leaving the force, served as chief of police at Cal Poly-Pomona, part of the California State University system, and represented Dorner during his internal personnel hearings within the Los Angeles Police Department.